md5sum of systems files

[jalogisch]

Run into issues several times that files that are part of the packages are adjusted on a local system and not replaced on the next upgrade.

That is mostly when the systemd overwrite files are not used for this, but the files are edited directly. As we know the md5sum of those files, we could check if any of these files have been changed to the origin to spot potential issues quicker.

This function should be used on remote connection or local run.